Connect your iPad to your Mac via USB, initiate the Mac's iTunes app and then sync the photos over to your iPad. Alternatively, you can install a USB type app like Phone Drive, Goodreader, Documents 5, etcetera, on your iPad, and then drag and drop the photos via iTunes.
If you're talking about the apple camera connection kit, then yes, you should be able to transfer them from the USB. The one caveat is that I believe they need to be in a folder named DCIM, just like on a digital camera.